Conventionally, use of a friction drive actuator for various moving devices has been tried. The friction drive actuator is generally comprised of a vibration member having a piezoelectric element which is an electromechanical energy conversion element and a sliding member for making contact with the vibration member in a pressurized state. The friction drive actuator is an actuator in which a relative movement between the vibration member and the sliding member in pressure contact with the vibration member is caused by an elliptical vibration (herein after, including a circular vibration) of a part of the vibration member, the elliptical vibration which is generated by inputting a drive signal into the piezoelectric element to expand and contract it.
The friction drive actuator is compact and excellent in silence, so that it is used as a drive mechanism for an electronic device such as an electronic camera, and in recent years, its applications have been spread more, and use thereof in a drive mechanism of a recording/reproducing head of an information recording apparatus such as a HDD and a DVD has been variously examined.
For example, there is known a vibration wave linear motor (a friction drive actuator) in which a vibration member is pressurized and held between two cylindrical guide shafts (sliding members), and due to an elliptical vibration generated in the drive contact portion of the vibration member, the vibration member and guide shafts make a relative movement in the axial direction (for example, refer to Unexamined Japanese Patent Application Publication No. 2005-57838).
Here, the schematic constitution of the vibration wave linear motor disclosed in Unexamined Japanese Patent Application Publication No. 2005-57838 will be explained by referring to FIGS. 10a, 10b. FIG. 10a is a front sectional view of a vibration wave linear motor 46, and FIG. 10b is a cross sectional view along the line D-D′ in FIG. 10a. 
On each of the upper and lower surfaces of a vibrator body 75, provided is a connection type drive contact portion 93 in which a flat portion 92 and a drive contact portion 76 are unified with each other. Two upper and lower guide shafts 77 (77-1, 77-2) in contact with recessed portions 76a of the connection type drive contact portions 93 are supported by upright members 78-2 of support members 78. The lower guide shaft 77-2 is pressed upwardly by a spiral spring 83, thus a vibrator 70 is pressurized and held between the two guide shafts 77. When AC voltages different in phase are applied to the vibrator body 75, the vibrator body 75 generates a vibration wave, and an elliptical rotation vibration is generated in the drive contact portions 76. By the elliptical rotation vibration, the vibrator 70 moves relatively to the two guide shafts 77 and support members 78 in the axial direction. By use of such a constitution, one part thereof is fixed, and the other part is connected to a driven member, thus the driven member can be driven to move.
Further, there is known a fine drive device (a friction drive actuator) for swinging a head arm (a sliding member) having a recording/reproducing head around a rotary shaft inserted through a rotation hole formed in the head arm, the drive device which is driven by an elliptical vibration generated in a vibration member in pressure contact with the head arm (for example, refer to Unexamined Japanese Patent Application Publication No. 2000-224876).
Further, there is known a rotary type ultrasonic actuator (a friction drive actuator) for rotating a rotor (a sliding member) born by ball bearings by a vibration member (for example, refer to Unexamined Japanese Patent Application Publication No. H06-78570).
Further, there is known an information recording/reproducing head drive device (a friction drive actuator) for swinging a head arm (a sliding member) around a V-shaped fulcrum formed in the head arm and supported by a wedge type support member by an elliptical vibration generated in a vibration member in pressure contact with the head arm (for example, refer to Unexamined Japanese Patent Application Publication No. 2001-222869).
On the other hand, in the information recording apparatus such as a HDD and a DVD, with the progress of higher recording density, the head drive mechanism is required to realize highly precise positioning of the head to the target position of a recording medium in submicron. Further, in correspondence with miniaturization and lower price of the information recording apparatus, further miniaturization and lower price are required for the drive mechanism.
In the vibration wave linear motor disclosed in Unexamined Japanese Patent Application Publication No. 2005-57838, as shown in FIG. 10b, the contact surfaces between the guide shafts 77 (77-1, 77-2) and the drive contact portions 76 are formed in a cylindrical shape with the same radius. However, when joining the two, unless the radii of the recessed portions 76a of the drive contact portions 76 are made larger than the radii of the guide shafts 77 (77-1, 77-2), and gaps are formed between the two, the two cannot be joined. Therefore, even if the two are processed highly precisely, gaps of microns are generated, and backlash is caused.
Further, the guide shaft 77-2 is supported by a bearing slotted hole 81 formed in the upright member 78-2 and is pressed up by the spiral spring 83. However, the support member is required to have a fitting backlash of microns, and an inclination of the vibrator 70 with respect to the guide shaft 77, which is equivalent to the fitting backlash, is generated and the relative position between the vibrator 70 and the guide shaft 77 fluctuates.
Therefore, in the vibration wave linear motor having such a constitution, due to various types of backlash of microns generated between the vibrator 70 and the guide shaft 77, it is difficult to set highly precisely the relative position between the two in microns which is required for the information recording apparatus.
Further, in the fine drive device disclosed in Unexamined Japanese Patent Application Publication No. 2000-224876, although the mechanism constitution is not described in detail, the head arm has a bearing mechanism of the rotary shaft, so that it can be inferred easily that backlash is caused in the bearing section. Further, the vibration member is structured so as to incline also in a direction other than the pressing direction, and for example, the head arm may rotate in a slightly twisted direction with respect to the rotary shaft. Therefore, there is a possibility that the head section provided at the end of the head arm may collide with the recording surface of the disk. Further, the constitution having no bearing mechanism is disclosed, though even in these constitutions, by the out-of-roundness and abrasion condition of the guide member and a shift of the shaft center due to a dent caused by an impact load, it may be considered that the positioning is affected greatly.
Further, in the rotary type ultrasonic actuator disclosed in Unexamined Japanese Patent Application Publication No. H06-78570, the members such as the ball bearings for bearing the rotor are used, so that backlash between the balls and the inner and outer walls cannot be avoided. The backlash component in the direction of the rotary shaft is biased, though the backlash component in the radial direction cannot be biased. These gaps are ones in microns and influence greatly the positioning. Further, at time of drive start of the vibration member, the gaps are first biased and then the drive in a desired direction is started, so that a problem arises that the startup characteristic is influenced. Further, when a highly rigid load support member is structured by such a mechanism, there is a possibility that complication and high price of the device due to enlargement of the apparatus and an increase in the mechanical parts may be caused.
Further, in the information recording/reproducing head drive apparatus disclosed in Unexamined Japanese Patent Application Publication No. 2001-222869, due to the pressure contact of the vibration member, the compression pressure to the V-shaped fulcrum by the wedge type support member is increased, thus there is a possibility that the fulcrum may be abraded. As a result, the position of the head mounted on the end of the arm is changed.